Apparatus for evacuating tubes



5 shaw-sheet.v 1

Sept. 19, 1944. w. w. EITEL ETAL APPARATUS FOR EVACUATING 'IQUBES Original Filed Dec. 30. 1942 INVENTORS WILL/AM W. E/TEL c/A CK MSCUjD-JH BY l si 7 THEIR ATTORNEY Sept-.19, 1944. w. w.E1TEL ErAv.V 2,358,567

APPARATUS EVACUATING TUBES Original Filed Dec. 30, 1942 '5 Sheets-Sheet 2' 4INVENTOR 5 WILLIAM hf- EITEL Q'CKA. IVI-CULL 06H BY THEIR ATTORNEY Sept. 19, 1944. w.- W. E11-EL ETAL 2,358,567

APPARATUS FOR EVACUATING TUBES Original Filed Dec. 30, 1942 5 Sheets-Sheet 3 INVENTORS WILL/AM M. EITEL JACK A. MSCI/L OUGH BY @I 7 THEIR ATTORNEY Sept. 19, 1944. w. W. l-:ITEL ETAL APPARATUS FOR EVACIYIATING TUBES original Filed nec. 3o, 1942 5 sheets-.sheet 4 INVENTORS WILLIAM w. E/TEL BJAc-'K A.4 M CCl/LLUGH .THEIR ATTORNEY Sept 19, 1944- w. w. EITEL ETAL 2,358,567

APPARATUS FOR EVACUATING TUBES Original Filed Dec. 30, 1942 5 Sheets-Sheet 5 emo ,/83 PLATE FILAMENT PowER POWER "76 66, POWER SUPPLY @Z SUPPLY SUPPLY I+ dr nnn 87 4d v v 1 v v v' INVENToRs w/LL/AM w. E/TEL To PUMP JACK A. MgCl/L uaH BY THEIR ATTORNEY Patented Sept. 19, 1944 UNITED STATES PATENT OFFICE APPARATUS FOR EVACUAITING TUBES William W. Eitel, San Bruno, and Jack A. Mc- Cullough, Millbrae, Calif., asslgnors to Eitel- McCullougli, Inc., San Bruno, Calif., a corpora.-

tion of California Original application December 30, 1942-, Serial No.

470,676. Divided and this application March `29, 1943, Serial No. 481,044,

9 Claims.

Serial No. 470,676, led December 30, 1942, in which is claimed the method embodying our invention, while this application is particularly directed to the apparatus.

, during the exhaust.

The invention possesses other objects and features of advantage, some of which, with the foregoing, will be set forth in the following description of our invention. It is to be understood that we do not limit ourselves to this disclosure of species of our invention as we may adopt variant embodiments thereof within the scope of th claims. l

Referring to the drawings:

Figure 1 is a plan view of apparatus embody, .ing the improvements of our invention, all of the carriages except;v one on the rotatable frame being merely indicated by dotted lines to simplify the view.

Figure 2 is a side elevational view of the frame, the carriages being omitted to show the central buss bar structure. n

Figure 3 is a fragmentary vertical sectional view, taken in a plane indicated by lines 3-3 of Figure 1, one of the carriages being included in full lines in this section.

Figure 4 is a detail elevational view looking at the front of one of the carriages.

Figure 5 is a detail sectional view of the oven, taken in a plane indicated by line ,5 5 of Figure 1. I

Figure 6 isa diagrammatic view showing the various connections to the buss bars.

In terms of broad inclusion, our apparatus comprises a movable frame for holding the tubes; means on the frame for exhausting the tubes; means for heating the tube envelopes; means for energizing the cathodes; andmeans timed with the frame movement for applying positive potentials to other electrodes for bombarding (ffl. 31632t) This is a division of our copendi'ng application,

them with electrons from the cathodes during predetermined periods of the tube travel.

In greater detail, the improvements embodying our invention will be described by first considering the apparatus and' then discussing its mode of operation. The novel methods involved will become clear as the description progresses.

Apparatus Referringv to the drawings, our apparatus comprises a rotatable frame or wheel having a rim 2 with spokes 3 terminating at a hub journaled about a vertical axis on a centrally disposed standard 4. The periphery of the wheel is additionally supported by rollers 6 under rim 2, several of these rollers being positively driven by motors 6 throughreduction gearings l to impart motion to the wheel. The rotatable frame or wheel is driven at a slow rate, depending upon the' time required to complete the exhaust of a tube. For purposes of illustration we will. take a four hour cycle, which means that the wheel will make one complete revolution in four hours. Fixed parts ofthe apparatus are supported by a main frame comprising pillars 8 carryingv a superstructure composed of triangularly arranged beams 9 and cross beams II.

Means are provided on the rotatable frame for carrying the tubes to be exhausted and the associated pumping equipment. For this purpose,

as shown in Figure 1, there are a plurality of say sixteen pie-shapedcarri'ages I2 arranged on the wheel. These carriages t side-by-side and together form a. circle coextensive withk the wheel. Referring to Figures 3 and 4, each carriage has a glass manifold I3 to which exhaust tubulationsv I4 of tubes I5 are sealed. Six tubes are shown on a manifold, but this may be varied depending upon the size of tube and capacity of the pump. With sixteen carriages carrying six tubes each, that makes a total of ninety-six tubes, it-being understood `of course that completed tubes are 'constantly being removed and replaced with new the specic arrangement of the leads will vary with different tube types. If the tube isV one having a base the latter is applied after exhaust,

as win be understood by those skilled in the art.

In order to facilitate servicing and repair, the individual carriages I2 are removably mounted on the rotatable frame, so that a carriage may be taken off a/nd replaced with another without holding up operation of the machine as a whole. As shown in vFigure 3 a carriage rests on rim 2 and also on al spoke 3 of the wheel, thereby giving adequate support yet allowing a given carriage to be slidably withdrawn from its nested position between adjacent carriages. The pie-shape of the carriages facilitates this withdrawal.

Means are provided on the carriages for evacuating the tubes on manifolds I3. With reference to Figure 3, a vacuum pump 23, preferably of the oil diffusion type is arranged on each carriage below manifold I3 and directly connected therewith. Arm 24 on the low pressure sidev of this pump is connected by a hose 26 through an oil trap 21 to a backing pump 28- which may be of a suitable mechanical type driven by a motor 29. In order to damp vibration of the mechanical pump the latter together with its motor is mounted on a plate 3I suspended in the carriage by springs 32. By this arrangement a self-contained pump unit is provided on each. carriage, operating independently of the other carriages. This gives adequate pumping capacity for the tubes on a given manifold, and, should a pumping unit fail, only those tubes on that carriage are affected. Withdrawal of the carriage removes the entire pumping unit for replacement or repair. An important feature of the improved apparatus, here to be noted, is that the vacuum pump travels with the tube. This eliminates any need for rotating joints or the like in the vacuum connections, which joints are practically impossible to keep vacuum tight. In our apparatus there is a positive direct connection between the tube and pump.

Means are provided .or heating the tubes during a portion of their travel on the rotating wheel. This heating is for the purpose of driving occluded gas out of the glass envelopes. As shown in Figures 1 and 5, an arcuately shaped tunnel-like oven 33 is arranged alongthe circular path taken by the tubes.

The oven is open at the ends and at the bottom so that the tubes on the manifold are able to pass through. This heating unit is suspended in fixed position from straps 34 on beams 9l of the main frame. The oven is fired by gas burners 36 arranged along the lower edges and fed by pipes 31 connected with suitable mixing and control devices. A 1ining 33 and an opening restriction plate 39 at each end conserves heat.

Means are further provided for energizing the electrodes of the tubes .to bring up the temperature of these parts for outgassingthem during exhaust. We accomplish this in our improved apparatus by supplying electrical energy to the tubes on the moving frame through a slidable contact mechanism including brushes, generally indicated by numeral 4I in Figure 3, mounted on the back sides of the carriages and engageable with fixed annular buss bars, generally indicated by numeral 42, disposed centrally of the machine. These buss bars are supported by insulators 43 on a circular subframe 44 rigidly suspended from cross bars II on the main frame. Brushes 4| are likewise supported on insulators 46 projecting from the back of the carriages, arranged in horizontal alignment with the buss bars.

4In the diagrammatic view of Figure 6 the buss bars are laid out in concentric circles to avoid confusion, it being understood that the bars have equal radii in the-actual machine. For further simplicity, connections to only v one tube are shown, and the power supplies are indicated diagrammatically. Numerous devices, such as switches, overload cut-outs, and various control means are omitted from thev diagram, since these are conventional devices and may be supplied wherever needed or desired as will be readily understood by those skilled in the art. The diagrammatic -view will be referred to in greater detail in the following discussion relating to the operation of our apparatus.

Operation Referring to Figure 1, the station between barriers 41 and 43 is provided for operators who seal ofi completed tubes from the manifolds and seal on new tubes to be evacuated. With a wheel rotating counterclockwise as viewed in .Figure 1, the seal-off operator works adjacent barrier 43. Based on a four hour cycle (the Wheel making one revolution in four hours), the time for a point on the wheel to travel from barrier 41 to barrier 43 is about 36 minutes, which gives ample time for the sealing operations. A suitable switch mounted on carriage I2 enables the operator to stop a pump motor 23 while sealing on new tubes.

Otherwise the vacuum pumps operate continuously during the cycle. A single tube will now be followed around the cycle since all tubes proceed in a like manner.

'I'he next period of tube travel, from barrier 43 to barrier 49, takes about 41 minutes, approximately 30 minutes of which the tube is in oven 33. An oven temperature of about 450 C. is preferably maintained. This is sufficient to drive occluded gases out of the glass envelope. Gases bleeding out of the walls into the interior of the tube are of course withdrawn by the pump. After leaving the oven the tube is cooled somewhat by an air blast from blower 5I.

The tube then travels between barriers 43 and 52, taking about 15 minutes. An operator work--` ing at this station hooks up the various connections with the tube leads. As shown in Figure 4, wire connectionshaving suitable clips are provided at the front of the carriage, including a wire 53 for engaging plate lead I9, a second wire 54 for engaging grid lead 2l, and a pair of wires 56 for engaging filament leads 22. These wires form part of circuit connections between the electrodes and the brushes. As seen in Figure 6, filament connections 56 are hooked to the secondary of a transformer 51, the primary of which is connected to brushes 53 and 53. Grid connection .54 terminates at brush 6I, and plate connection 53 terminates at brush v62. Another connection 63 is made between the filament circuit and still another brush 64, this connection and brush being for the purpose of completing the plate and grid circuits so that space current will flow. While the brushes all happen to be shown in contact with buss bars in Figure 6, it vis understoodv that there are times when the brushes are not riding on the bars. In fact, all the circuits are open along the path of tube travel between -barriers 41 and 52, .by reason of the absence of sections in the buss bars between these points.

After passing barrier 52 from the hook-up station the filament I6 of the tube is energized. In a tube having a 5 volt lament of thoriated tungsten the filament is preferably brought up by applying 3 volts for about 1/2 minute. then ashed at 8 volts for about 21/2 minutes, and then held at about 7 volts for the remaining period v potential applied to the grid during this prelimof the exhaust procedure. Filament current is l supplied from a suitable source 88 of alternating current through buss bars associated with brushes 58 and 59. One of the bars 61 is a continuous ring connected with the source by a feeder 88.

. The other bar is split into three segments comprising two short segments 69 and 18, and a long tail segment 1I, Segments 10 and 1I are supplied with the required potentials fromsource 89 through feeders 12 and 13, the voltage being example, with a tube having a cage-type platinum grid and a cylindrical tantalum plate 3A, inch in diameter and 1 inch long, the total outgassing period is about 138 minutes. This together with the speed of the rotating frame or wheel determines the length of segment 1I, as will be readily understood.

After the lament has been flashed the plate I8 is heated to a predetermined temperature for a preliminary outgassing period. In the tantalum plate tube taken for example the plate is gradually heated over a period of about 30 minutes to about 1400* C.; this and other electrode temperatures mentioned herein being brightness" temperatures as read on an optical pyrometer scale. The heating is accomplished by applying a positive potential to the plate -to cause bombardment thereof by electrons evaporated from the Illa-ment, the heat being due to the energy given up to the plate when thelast moving electrons are suddenly stopped. Positive potential is supplied from a suitable source 16 of direct current through buss bars associated with brushes B2 and 84. One of the bars 11 is a continuous ring connected with the negative side of the source by a feeder 18. 'Ihe other bar includes three leading segments 19 connected by feeders 8|v with different potential levels at the positive side of the source, the positive potentials applied tothe plate increasing at say 10 minute intervals as the brush advances from segment to segment. These potentials are adjusted to elevate the tantalumv plate to the temperature above mentioned. In order to prevent excess plate current from flowing due to gas ionization in the tube, suitable resistors 82, such as lamp banks, are interposed in lines 8l. After brush 62 leaves the third segment there is an interval when no potential -is applied to the plate.

During this interval grid I1 is heated to a predetermined temperature for a preliminary outgassing period. In the platinum grid tube taken for example the grid is heated to about 1300 C. for about 6 minutes. Positive potential is applied to the grid from a suitable source 83 of direct current through buss bar 11 (which is common to both sources) and through another buss bar associated with brush 6l. The latter bar includes three short leading segments 84 connected to the positive side of source 83 by lines 86. These lines are all connected together, but the two going to the rst two segments include lamp bank resistors 81 for limiting current in event of excessive gas ionization. The positive by lines 9| and 92.

mary heating period is adjusted to elevate the platinum grid to the temperature above men tioned.

Next, both the plate and grid are heated simultaneously for a prolong'ed period of about 100 minutes, the plate beingmaintained at about 1400 C. and the grid at about 1250 C. This is accomplished by long tail segments 88 and 89 of the plate and grid buss bars, these segments being connected to the respective power supplies The positive potentials applied to the plate and grid are adjusted to maintain the above temperatures, as will be readily understood. Since the initial burst of gas was removed from the electrodes during the preliminary heating periods, there is little danger of excessive gas ionization during the s'ubsequent prolonged heating period, and therefore it is unnecessary to provide current limiting resistors in lines 9| and 92. The simultaneous heating of the electrodes for the time and at the temperatures above speciied removes substantially al1 of the releasable gases from the tantalum plate andplatinum grid. It is understood that during all of these outgassing periods the vacuum pump is'operating continuously. After the simultaneous heating period th platinum grid is preferably heated for an additional period of about 2 minutes. This iinal clean-up of the grid alone is not alwaysnecessary, but the step is preferably included t o insure removal of residual traces of gas. As shown in Figure 6, the grid buss bar 89 is slightly longer'v than plate bar 89, to continue application of potential to the grid for the period' above stated. The lament buss bar 1l is of course coextensive with grid bar 89.

It is understood that the above pumping schedule is merely given as an example to illustrate the operation of the machine. The pumping schedule may be varied within wide limits, depending upon the type of tube and thesize and character of electrodes therein. This will be obvious to those skilled in the art. Thus, it may be desirable to outgas the grid before the plate during the preliminary heating periods, in which case segments 84 of the grid buss bar would be located ahead of plate bar segments 19. The length of the heating period for any given electrode or electrodes may be varied by increasing or decreasing the length of the buss bar segments. In any case the buss bars and associated brushes provide means for automatically timing the electrode heating periods with the progressive movement of the tubes. f

Heat treatment of the electrodes ceases as brushes 59 and 6l ride off buss bar segments 1I and 89, all of the circuits to the electrodes being opened by this time. A tube then advances in front of a blower 93 (Figure 1) to cool the en, velope for subsequent handling. Finally the tube passes barrier 41 into the station where an operator removes the tube by sealing oil tubulation i4.

From the foregoing it will be seen that our method involves moving the tube along a path,

and, while the tube is in motion, exhausting it` 'whereby a greater degree of uniformity is attained between tubes. Since completed tubes are constantly being removed and replaced by new ones,` the exhaust process is a continuous one, well adapted for large scale production. Furthermore the mounting of the vacuum pump for movement with the tube eliminates the need for rotatable joints or the like in the vacuum line, thereby materially improving the degree of high vacuum attainable in the tube. This together with the automatic timing of the exhaust procedure produces superior tubes having uniform characteristics.

We claim:

1. Apparatus for evacuating a tube having an envelope enclosing a cathode and another electrode, comprising a ilxed frame, Ia movable frame, tube holding means on the movable frame, a vacuum pump on the movable frame connected to said envelope, a source of cathode heating current, circuit means connecting said source with the cathode, a source of direct current potential having positive and negative terminals, and circuit means connecting the negative terminal to the cathode and the positive terminal to said other electrode, both of said circuit means including slidable contact mechanism interposed between said movable and xed frames.

2. Apparatus for evacuating tubes, comprising a movable frame, a plurality oi' carriages on the movable frame, a separate manifold on each carriage to which tubes are connected, and a. vacuum pump on each carriage connected to the manifold thereon.-

3. Apparatus for evacuating a tube having an 35 envelope enclosing a cathode and another electrode, comprising a movable tube support, an exhaust device for exhausting the envelope while the tube is carried by said support, means energizing the cathode, and an electric circuit in- 40 cluding connections applying a positive potential to said other electrode during said exhaust.

4. Apparatus for evacuating a .tube having an envelope enclosing a cathode and grid and plate,

comprising a movable tube support, an exhaust 45 5. Apparatus for evacuating a tube having an envelope enclosing a cathode and a plurality of other electrodes, comprising a movable tube support, an exhaust device for exhausting the envelope while the tube is carried by said support,

.means energizing the cathode, and an electric circuit including connections selectively applying positive potentials to said other electrodes during predetermined periods of said exhaust.

6. Apparatus for evacuating a tube having an envelope enclosing a cathode and another e1ectrode, comprising a movable tube support, an exhaust device vfor exhausting the envelope while the tube is carried by said support, means energizing the cathode, and an electric circuit including connections movable with said support applying a positive potential to said other electrode during said exhaust.

7. Apparatus for evacuating a tube having an envelope enclosing a cathode and another electrode, comprising a. movable tube support, an exhaust device for exhausing the envelope while the tube is carried by said support, means energizing the cathode, and an electric lcircuit including connections applying a positive potential to the other electrode during the exhaust, said connections including a slidable contact mechanism.

8. Apparatus for evacuating a tube having an envelope enclosing a cathode and another electrode, comprising a movable tube support, an exhaust device for exhausting the envelope while the tube is carried by said support, means energizing the cathode, and an electric circuit including connections applying a positive potential to the other electrode during the exhaust, said connection including a ilxed buss bar and an associated brush movable with the tube.

9. Apparatus for evacuating a tube having an envelope enclosing a cathode and at least two other electrodes, comprising a movable tube support, an exhaust device for exhausting the envelope while the tube is carried by said support, means energizing the cathode, and an electric circuit including connections applying a positive potential to first one and then another of said other electrodes during said exhaust.

WILLIAM W. EITE'L. JACK A. MCCULLOUGH. 

